Variable Interest Entities (Details) - USD ($) $ in Thousands		Dec. 31, 2024	Dec. 31, 2023
Variable Interest Entity [Line Items]
In-service utility plant, net		$ 2,149,138	$ 2,018,121
Construction work in progress		138,208	110,091
Accrued interest and accrued (prepaid) taxes		11,558	9,372
Deferred income taxes		316,397	279,029
Unamortized discount and debt issuance costs		4,419	4,579
MGE Power Elm Road [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		159,576	162,210
Construction work in progress		514	834
Other Receivables		$ 0	$ 0
Other Receivable, after Allowance for Credit Loss, Related Party [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ (184)	$ 376
Deferred income taxes		30,902	30,502
Long-term debt	[1]	41,082	43,714
Noncontrolling interest		104,304	103,751
Unamortized discount and debt issuance costs		200	300
MGE Power West Campus [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		76,378	75,392
Construction work in progress		3,052	1,533
Other Receivables		$ 911	$ 2,550
Other Receivable, after Allowance for Credit Loss, Related Party [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ (78)	$ (22)
Deferred income taxes		15,435	15,249
Long-term debt	[1]	28,550	31,019
Noncontrolling interest		46,082	45,780
Unamortized discount and debt issuance costs		$ 100	$ 100

[1] MGE Power Elm Road's long-term debt includes debt issuance costs of $0.2 million and $0.3 million, respectively, as of December 31, 2024 and 2023. The debt is secured by a collateral assignment of lease payments that MGE makes to MGE Power Elm Road for use of the Elm Road Units pursuant to the related long-term leases. MGE Power West Campus's long-term debt includes debt issuance costs of $0.1 million as of December 31, 2024 and 2023. The debt is secured by a collateral assignment of lease payments that MGE makes to MGE Power West Campus for use of the cogeneration facility pursuant to the long-term lease. See Footnote 14 for further information on the long-term debt securities.